Painkiller Hell & Damnation is on sale for 75% off as the GameStop daily deal for 5/9/13.
Painkiller Hell & Damnation = $4.99 (Steam)
Painkiller Hell & Damnation Collector’s Edition = $7.49 (Steam)
Dark Souls: Prepare To Die Edition is on sale for $14.99 (50% off). Requires Steam activation (and GFWL).